Field of the Invention
The present disclosure relates to a random number generating apparatus,
Description of the Related Art
Use of random, numbers is essential in the information security field. In recent years, a high-performance random number generating apparatus has been highly demanded which can generate true random numbers having uniformity (without differences in probability values and incidences of random numbers) while without regularity of incidence, correlation and periodicity of the numbers.
A generally known random number generating apparatus applies high-speed operating clocks output from a ring oscillator and has the following configuration.
The high-speed operating clocks output from the ring oscillator are connected to a data input terminal of a flip-flop circuit (hereinafter, an FF). Clocks which are asynchronous with the clocks output from the ring oscillator and which have a low frequency and contain a large jitter component are connected to a clock terminal of the FF to operate the FF.
Thus, due to influence of a jitter component of the high-speed clocks from the ring oscillator and a jitter component of low-speed clocks input for synchronization of the FF, random numbers are generated from the output from the FF.
A technology has been proposed which may XOR outputs from a plurality of ring oscillators and thus increase the number of times of toggling of signals to be input to a data input terminal of an FF or may provide a plurality of ring oscillators having different delay times and thus select the cycle or jitter value of clocks to be generated so that a configuration with high randomness can be selected (as in Japanese Patent Laid-Open No. 2001-184255).